Giles MacDonogh is a bon viveur and a historian of wine and gastronomy, but in this book, pursuing his other consuming interest - German history - he serves a dish to turn the strongest of stomachs. It makes particularly uncomfortable reading for those who compare the disastrous occupation of Iraq unfavourably to the post-war settlement of Germany and Austria.

MacDonogh argues that the months that followed May 1945 brought no peace to the shattered skeleton of Hitler's Reich, but suffering even worse than the destruction wrought by the war. After the atrocities that the Nazis had visited on Europe, some degree of justified vengeance by their victims was inevitable, but the appalling bestialities that MacDonogh documents so soberly went far beyond that. The first 200 pages of his brave book are an almost unbearable chronicle of human suffering.

His best estimate is that some three million Germans died unnecessarily after the official end of hostilities. A million soldiers vanished before they could creep back to the holes that had been their homes. The majority of them died in Soviet captivity (of the 90,000 who surrendered at Stalingrad, only 5,000 eventually came home) but, shamingly, many thousands perished as prisoners of the Anglo-Americans. Herded into cages along the Rhine, with no shelter and very little food, they dropped like flies. Others, more fortunate, toiled as slave labour in a score of Allied countries, often for years. Incredibly, some Germans were still being held in Russia as late as 1979.

The two million German civilians who died were largely the old, women and children: victims of disease, cold, hunger, suicide - and mass murder.

Apart from the well-known repeated rape of virtually every girl and woman unlucky enough to be in the Soviet occupation zones, perhaps the most shocking outrage recorded by MacDonogh - for the first time in English - is the slaughter of a quarter of a million Sudeten Germans by their vengeful Czech compatriots. The survivors of this ethnic cleansing, naked and shivering, were pitched across the border, never to return to their homes. Similar scenes were seen across Poland, Silesia and East Prussia as age-old German communities were brutally expunged.

Given that what amounted to a lesser Holocaust was unfolding under their noses, it may be asked why the western Allies did not stop this venting of long-dammed-up rage on the (mainly) innocent. MacDonogh's answer is that it could all have been even worse. The US Treasury Secretary, Henry Morgenthau, favoured turning Germany into a gigantic farm, and there were genocidal Nazi-like schemes afoot to starve, sterilise or deport the population of what was left of the bombed-out cities.

The discovery of the Nazi death camps stoked Allied fury, with General George Patton asking an aide amid the horrors of Buchenwald: 'Do you still find it hard to hate them?' But the surviving inmates were soon replaced by German captives - Dachau, Buchenwald, Sachsenhausen and even Auschwitz stayed in business after the war, only now with the Germans behind the wire.

It was Realpolitik, not humanitarian concern, that caused a swift shift in western attitudes towards their former foes. Fear of Communism spreading into the heart of Europe, and the barbarities of the Russians - who kidnapped and killed hundreds of their perceived enemies from the western zones of Berlin and Vienna - belatedly made the West realise that they had beaten one totalitarian power only to be threatened by another.

Even that hardline Kraut-hater Patton was sacked for advocating a pre-emptive strike against Russia. Building up West Germany and saving Berlin from Soviet strangulation with the 1948 airlift became the first battles of the Cold War - even if that meant overlooking Nazi crimes and enlisting Nazi criminals in the 'economic miracle' of reconstruction.

Although MacDonogh roundly condemns all the occupying powers, the British emerge with some credit. Apart from one Air Marshal who looted art treasures; and an MI5 interrogator nicknamed 'Tin Eye' Stephens who ran a private torture chamber, British hands may have been grubby, but were not deeply blood-stained. British squaddies preferred to purchase their sex privately with a packet of fags or a pair of nylons, rather than in the Soviet style.

MacDonogh has written a gruelling but important book. This unhappy story has long been cloaked in silence since telling it suited no one. Not the Allies, because it placed them near the moral nadir of the Nazis; nor the Germans, because they did not wish to be accused of whitewashing Hitler by highlighting what was, by any standard, a war crime. Giles MacDonogh has told a very inconvenient truth.